Christof, it turns out I spoke too soon. The problem is back--in a slightly different form. I was motivated by all the above to set up Terminal Services on my own network file server and so can test more quickly now without outside help. Testing instigated by further trouble reports from customers reveals that I'm still getting a TABLEUPDATE failure, but only if two users SAVE at exactly the same time in separate TS sessions on the same server. If two users add records simultaneously but save separately, no problem occurs, but saving simultaneously, whether the APPEND BLANK actions took place simultaneously or not, results in the failure. The use of DELETED records has been eliminated, APPEND BLANK is used every time. AERROR after the TABLEUPDATE reports 109, "Record is in use by another user."

My SaveChanges method calls TABLEUPDATE(1,.F.,lcAlias) first and if that fails, drops into a Resolve method which checks for conflicts field by field and then calls TABLEUPDATE(.F.,.T.,tcAlias) to (attempt to) force the update. Both TABLEUPDATEs fail, and the Resolve method shows NO field conflicts, i.e., my unique ID code is working fine. Write caching on the file server has been turned off. I'm using optimistic table buffering.

Any further ideas?